And natural boolean between volumes don't can give some result ?

Does all that is real pieces or imaginative stuff ?

First, as I said, the "parts" here are dictated by their functions. One of the reasons that I posted this is that a lot of what is done with MOI is aesthetic -- that is, the object is to make something Look a certain way. My work has to be turned into machine parts that have to function, and not just look nice. That object that you did the rendering of is part of a piston, which will see 9,000-rpm in that cylinder. The problems then are quite different. One "part" has to do one thing and the next "part" has to do something else. But these "parts" have to come together into One Part. Without understanding what the engine does, how it operates, you can't appreciate Why every detail of this cylinder must be very nearly as it is. And when I put these "parts" together, I can't compromise their function in order to accommodate the limitations of the software I'm using. And the beauty of MOI is that I don't have to compromise. But there may be other ways of getting the job done. I haven't seen anyone else solving the sorts of problems that I have to solve, so I developed my own techniques. I would be very happy if someone could show me an easier, faster way to do this. But what I've found on the Forum are people getting stuck doing things that I think are trivial. I must point out that in this last example, when I look at the "parts" that I must bring together, there is no one solution to the problem. This is why I have to draw a bunch of lines and keep trying different ideas until I find something that works. And solving this problem doesn't help much when I get to the next configuration -- every arrangement is different and requires a unique solution. But my method always works.

Many thanks for your always very detailed explanations!

PS Can we say that your method is a little like the option "Planar Sections" of the Blend function ?
http://moi3d.com/forum/index.php?webtag=MOI&msg=6790.35

I haven't used the Planar Sections option -- but I thank you for suggesting it! There are still some complex geometries that take a lot of time to get right. The Planar Sections option might help in such cases. The main technique that I wanted to offer is that where I can draw rough curves on a surface in order to 'see' what I want to do next. Then, use Project -- from an appropriate plane -- to get a fair curve that is actually on the surface. That curve is adjusted and used to trim the surface. All this must be done Before using 'Blend', as you have to have corresponding edges to work with. I also want people to understand that the limitations of 'Blend' and 'Network' can be largely overcome by using both of them together. There are several other tricks that I use but did not mention. 'Network' has a tendency to curl the surface as it approaches an edge. To fix that, I usually use 'Iso' to give me some curves that lie on the not-quite-right surface. I often 'Rebuild' these curves, reducing the number of points, which washes out a lot of minor distortions. Then, I adjust the points on these curves, near the curled edge, so that they are tangent to the surface. The trouble with 'Network' is that it doesn't take into account the form of adjacent surfaces, so we have to provide enough information so that those intersections will be tangent; and this is what I'm talking about. When I have those new curves corrected, I run 'Network' again and the curl at the edge is gone. I didn't mention a problem with 'Blend'. You have to break up a 'fillet' at every intersection, as you cannot add edges (as you can with 'Network'). And when the geometry is complicated, those short sections of Blended 'fillets' don't fit together well. They may look okay from a distance, but it you zoom in, you will find that there is a gap or the edges overlap. But if you use those Blends only to give you cross-sections (which are properly tangent to the adjacent surfaces), then delete those Blends and run 'Network', everything fits without errors.

Thanks for these extra infos!

Just a little thing ;)
The position of the click of the Blend function gives not the same result!
That was the same for the surfaces in the past but as that was some perturbating i believe that Michael stop it!

Only subsists that for the curves! ;)



PS Of course i have forgotten the normal way ;)

You asked about 'Joining' the surfaces of the cylinder model. As I said, the model shown was just to look at. One thing that I did in that regard was to make curves of all the edges that I want to be seen as edges; then I gave them a different color. This looks much better than otherwise. Of course you want to hide all the edges of surfaces that should look continuous. But when you hide the edges, the edges that should look like edges become sort of fuzzy. To change the model for 3D printing, I eliminated all those curves, so that I had only surfaces. I also eliminated all the 'holes' (screw holes) which were open on the bottom. I then 'Joined' the surfaces. Only one had a problem! Think about that: More than 1400 surfaces in this model and only one problem. That surface was a simple one and I redid it in a few seconds. Then the whole cylinder was one joined-object. Let me say again that my method is to 'Project' a line onto a surface. Then, I move the endpoints of that line to the intersections of the surface. This eliminates a thousand errors that prevent the edge of one surface from matching the edge of the next surface. Only then do I use this line to 'Trim' the surface. Also, as I said, 'Blend' will frequently mismatch the edges of fillets, where more than one 'Blend' is required. Using 'Blend' to make cross-sections, and then using 'Network' to build the fillet eliminates those errors. When I started with MOI, I was doing what I thought should work, but when I zoomed in, I found too many mismatched endpoints. How could I avoid these? I found that the best way was always to begin with a line, adjust the endpoints, then 'Trim'. This is how I produce more than 1400 surfaces without errors.

Another cool explanation!

<< 'Project' a line onto a surface. Then, I move the endpoints of that line to the intersections of the surface.

a projection don't put the extremities of a curve at the intersection of the surface ?


else ...
What will your strategy for this little case where fillet don't work ?

http://moiscript.weebly.com/uploads/3/9/3/8/3938813/fil_dont.3dm

__As to your first question. In many cases, you might not project a curve, but instead, in one of the orthographic views, cut the surface directly. This saves a step, so why bother to project the curve and move the endpoints? Well, I started out doing it that way, and I found that too often I ended up with spurious endpoints; that is two or more "endpoints" very close together. Which one is the "right" one? In some cases, I ended up with three or four "endpoints". This led to all sorts of problems, so I had to find a way to work so that I only had one true endpoint or intersection. I can't tell you why we get these errors. In theory, the points should work out right, but in practice these errors keep coming. I call them "rounding-off errors". In any case, when I project lines and adjust the endpoints, I eliminate the errors.
__As to your fillet problem, this was simple. First, I copied the cylinder where you had projected the curve and cut the hole. Then I copied the other part and aligned them. I then made the blue curves and did a 'Blend' between them. This is using 'Blend' with curves only, not surfaces. I then projected the red curves onto both objects and did another 'Blend' between them. Now I could use 'Network' with three true cross-sections between the two objects. It's the same, top and bottom. You can see the result with the edges hidden. It's not quite perfect. One more step would project two more lines and due two more blends to get two more cross-sections, between the ones that I did the first time. You have to give 'Network' enough information to work with. In this case, only one cross-section between the ends of the fillet is not quite good enough. Obviously, if I wanted to I could add as many more cross-sections as I thought necessary, but you can see that only one (between the ends) looks good and you have to look closely to see that between those sections 'Network' has exercised a bit too much "imagination".

Many thanks!

I believe that I have quasi all understood this time!
And sure blend the lateral blue curves gives a better result than my manual drawing!

Maybe a method can increase the speed process
Add cut point(s) on the "edge(s)" (not the curves) for have 2 parts or more for make Blending surfaces (in easy cases) or Network!
That avoid to cut volumes!
All surfaces in this follow easy case will make a "solid" even with the "Blending surfaces" !

__What I've tried to convey here is the use of 'Project', 'Blend', and 'Network'; which together can solve almost any problem. There are other tools that are useful, and in many simple cases another method may be quicker. But when you have a problem that you cannot solve using your own methods, this technique will work. I've been using this on thousands of cases of every configuration and I always get the result that I want. But what can't be taught is how to use this method to solve a Specific problem. These are of infinite variety and only experience will help a person see how to proceed. Too often, I go about something in the wrong way, with a poor result. But when I know what Not To Do, I am a big step closer to seeing the right approach. In the problem that you gave me, you tried a few things that didn't give you what you want. I looked at it and immediately saw how I could blend a couple of lines that would serve as cross-sections for 'Network', and gives a good result. That's what can't be taught; that's all about experience. But I'm still learning!
__I'll give you one more tip. When using 'Network', 'Normal' sometimes gives a lumpy surface. 'Lighter' smooths it out. (I guess that's why it's there!) BUT, 'Lighter' often pulls the edges away, so that the edge of one surface doesn't fit the edge of an adjoining surface -- even though the endpoints are good. This is exactly the sort of condition that you want to avoid, so it is best to use 'Normal'. In cases where 'Normal' gives a lumpy surface, there are two ways to fix it. First, use 'Iso' to map a grid onto the 'Normal' surface. 'Show Points' on the grid, and you will see that there are too many points -- which are necessary to define all the little bumps and hollows. So, with the whole grid selected, 'Rebuild' the curves, going from maybe 30 points to 6 or 8. Then delete the surface and run 'Network' again. In this way you have eliminated a lot of information that was responsible for the surface irregularities. In really bad cases, you can do this process more than once, each time washing out irregularities and smoothing the surface. The second method is to use 'Lighter'. Then Iso a grid onto that surface. Delete the surface. Now, one by one, move each endpoint of the grid 'On' to the corresponding edges (which corrects the errors that 'Lighter' introduces). Then run 'Network' again in 'Normal' mode and you will get the cleaner surface of 'Lighter' without the edges pulling away.
__And here is something that you may not have tried. Say that we have a four-sided hole to fill between four other surfaces. ('Network' only works with three or four sides -- so if you have five sides, you have to subdivide the area before you can use network.) Now, let's say that you have a grid of four curves. These intermediate sections do not have to stop at the edges of the adjoining surfaces! They can continue onto those surfaces and thereby insure that the new surface will be tangent to the existing surfaces. It appears that 'Network' calculates the surface form differently if these intermediate curves stop at the edges or continue beyond the edges. Try it both ways and see how it works. As to how you get those intermediate curves to fit the adjacent surfaces and pass over the empty space of the hole that you want to fill, here is where 'Blend' comes in again. You can trim edges into short sections, and use 'Blend' between those sections. Change one edge of this narrow blend into a curve, then delete the narrow surface and you have a cross-section that is tangent to the surfaces. Remember that you can vary the 'Bulge' factor from one cross-section to another, which gives you great control over the form of the surface (but can also give a wavy surface if you have different bulges too close together or radical differences in bulge factors that don't fit well with the existing surface edges!). The amazing thing is that, even when you define an irregular form, 'Network' will produce it. This is the price paid for creative options: You can do bad as well as good!

Another cool advices!

Here is another example. When several forms come together in complex relationships, integrating them is a serious problem. Some of the programs that use polygons may be faster for relatively simple jobs, but when things get complicated, they fail. MOI can deal with anything, but you have to go about it in the right way. 'Project' is a powerful tool that is probably not used much. 'Blend' and 'Network' are probably used separately, when they work best together. Use all three together and the results are really impressive.

oops i posted this before refreshing the page.......lol....this looks like i will understand......................its still not completely clear to me. i get the idea of using the different tools....i wonder if you could make a simpler example and do a screen grab with each stage instead of so many words.....my mind is more visual learning....understand your busy so just if you get a chance.

great work Sir

Neil

My words exactly! it's difficult to fully understand just through words. So small video would be great if you ever find the time.

I know that a video would be very helpful, but -- even if I had time to do this -- I don't know how. My work is in engineering, and MOI is a most important tool that I use. I marvel at what you guys do with computer graphics, and that's because I'm clueless in this area. However, if you go back and look at the pics that I posted here, and the explanations, Then Practice, I think it will all become clear. When you have two or more surfaces that don't fit together, you have to create gaps between them, that can be filled using 'Blend' and 'Network' together. So, the first step is to "Project" curves onto the surfaces. The beauty of 'Project' is that your projected curves may not be quite right. But your curve-to-project only has a few points, and After the Projection, if you move those points, the projected curve moves in accord. So you can keep playing with the curve on the Plane until the projected curve is just what you want. The most important trick that I wanted to show here is how to create a rough curve on a Plane that is at an appropriate angle to the surface to be projected onto. Sometimes you can use the orthogonal views, but often, the surface is at an odd angle and you need to set up a Plane at a corresponding angle. I gave you a picture that you should study, as this shows such a Plane and the lines that translate the curves between the surface and the plane. When I started this, I thought that I would have to reset the 'C-Plane' to the new odd-angle plane, but this is rarely necessary. MOI automatically 'Projects' perpendicular to the Plane -- except in rare cases, and if it doesn't Project, then set the 'C-Plane' and it will work. Don't forget to reset the endpoints of the projected curve before trimming the surface -- this eliminates a lot of spurious endpoints. Another reason that I posted this technique is that I hoped that someone with more experience would tell me that there is an easier way to get the same results. Nobody has come forward, so I am assuming that my method is unique. AND, if this is true, then I have to say: if you don't know how to do this, you are going to run into a multitude of complex problems that you cannot solve. IF you know how to do this, you can do anything!

Do you use more Project Mode "Direction" or "Closest Pt" ?

hi Tim,

i was wondering if you could show some images of what you mean about pulling away projected curve end points...your method has me excited to learn from your wisdom and skip the headaches you spoke about extra endpoints errors.


best Regards neil

__Pilou, I always use 'Direction'.
__Regarding endpoints: In some cases, in the orthogonal views (or if you set the 'C-Plane') you can draw a curve and use that directly to Trim a surface. That seems the easier way. However, you are then stuck with that result, or you can undo it and go back to where you were. When you project a curve, all you have is a line on the surface, which you can still modify. One modification is to 'Show Points' on that curve. Go to each endpoint, and sort of drag it (hold the mouse button down and move it a little bit). That endpoint of the curve will then Snap to the intersection of the surface(s). Ideally, when it Snaps to the intersection, you will see "End, Int". If you wiggle around here and you see "End", and then "Int", then "End, Int", that means that there is not a clean intersection there. When I used to Trim surfaces directly, as I said at the beginning, I often had these multiple, not coincident, intersections. Then, when you select a point here later, which do you want, "End", "Int", or "End, Int"? If you look down at the coordinates, you often see that as it jumps between "End" and "Int", there will be a difference, maybe only 0.001, but that's enough to cause you trouble. If you project a curve and reset the endpoints, you eliminate these errors. As I said before, I think these are due to rounding off calculations. When you set the endpoints of a curve by Snapping to the intersection of the surface, there is no rounding off (or maybe it would be more correct to say that all the possible points are rounded to the same number).
__Another advantage of Projecting a curve (rather than trimming it directly), is that you can look at it from different angles and see if that is really what you want. If it's not, you can move the points on the original curve, on the plane, and the projected curve will follow it. This is a great advantage. The only time this doesn't work is if you project onto a cylinder, or something, where there are two sides and the projection produces two curves. In that case, moving the points on the plane, after the projection, won't work. I guess manipulating two curves at once is too difficult. But please just project a curve onto a surface and then move the points on the plane and watch what happens. BTW, you want to keep the point count as low as possible on the curve-to-project. Four or five points is usually enough, and then you can adjust those points and keep the curve fair. If you show points on the projected curve, it might have 50 points! It needs that many to keep the curve on the surface. You can't manipulate a bunch of points without making a mess. So what you are doing in effect, is moving a few points on a flat plane, and at the same time manipulating 50 points on a surface with compound curvature! It's very powerful.